JPH01201083A - Refractory castable for injection lance for out-furnace refining - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance and spalling resistance of a refractory castable to a slag of a relatively wide basicity range, by adding specific binding material and gelling assistant to a refractory raw material composed mainly of zircon. CONSTITUTION:The objective castable can be produced by compounding (A) 50-95% (in terms of ZrO2:SiO2) of a refractory raw material composed of zircon and/or a zircon raw material with (B) 1-5% (in terms of solid) of colloidal silica having particle diameter of 0.01-0.02mum as a binding material, (C) 0.5-5% of alumina cement as a gelling assistant and, as necessary, (D) 3-40% of silica agalmatolite as a material for imparting residual expansibility, (E) a deflocculant (e.g. sodium tripolyphosphate), (F) 2-3% of vapor-phase silica fume and (G) <=2vol.% of stainless steel fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides a refractory castable for lining a flux injection lance in the out-of-furnace refining of molten steel.

In recent years, due to the demand for higher grade steel products, after steel is produced in a converter, desulfurization and dephosphorization are carried out in a ladle. In order to do this, a lance vibrator protected by a refractory is immersed and treatment flux is blown into the steel. ing.

(Prior technology) The lining material for this injection lance is required to have slag resistance and heat spall resistance because it comes into contact with high temperatures and corrosive slabs. Castable is used.

Since conventional alumina castables have poor spall resistance, an attempt has been made to improve the alumina-carbon castable refractories for lances disclosed in JP-A-61-236656 by adding carbonaceous raw materials.

(Problems to be Solved by the Invention) However, under conditions where carbonaceous raw materials are repeatedly immersed and left in the atmosphere, as in the case of a lance, oxidation progresses rapidly, which tends to lead to a decrease in corrosion resistance.

In addition, although corrosion resistance improves as the alumina content increases and basicity increases, heat spalling resistance tends to deteriorate.

On the other hand, zircon is the only natural raw material consisting of zirconia and silicic acid, and its melting point is as high as 2015℃, and it has a small coefficient of thermal expansion, no transformation, and excellent thermal spalling properties. It is widely used as a furnace material for steel making such as steel mills.

The superiority of zircon materials is also stated in JP-A-59-102866, which targets refractories for ladles, tundish linings, and lance pipes, but this pertains to shaped refractories. , which is different in character from the monolithic refractories that are the object of the present invention.

Although zircon has high refractory properties, it dissociates at 1540°C, and the Fuller 2x component (A
1 203 , Cao, R20) has the drawback of lowering the dissociation temperature and suppressing re-zirconation, which tends to cause structural spalls.

Therefore, the object of the present invention is to make use of the characteristics of zircon raw material which has excellent corrosion resistance against a relatively wide range of #1 base slags, and to compensate for the drawbacks, thereby creating a material with excellent corrosion resistance and spalling resistance. An object of the present invention is to provide a refractory castable for an injection lance for out-of-furnace scouring.

(Means for solving the problem) As a result of intensive research in order to improve the above-mentioned drawbacks, the present inventor used colloidal silica as a binder for a refractory raw material mainly composed of zircon, and used alumina cement as a gelling agent. By doing so, we have found that the components that cause a decrease in fire resistance can be suppressed to an extremely low level, and we have achieved an improvement in structural spall resistance that could not be solved with conventional technology.

Refractory raw materials made of zircon (sintered zircon, etc.) and zircon raw materials (zircon sand, zircon flour, etc.) are
Its content is 50 to 95% in terms of ZrO2/SiO2 amount.
If the content is less than 50%, the corrosion resistance will be poor, and if it exceeds 95%, residual expansion property cannot be obtained.
It is 0-80%.

Colloidal silica used as a binder has various concentrations (20 to 50% as a commercial product), but any concentration may be used, and the amount added is 1 to 5% in terms of solid content, preferably 2.
~3% is good, less than 1% is ineffective as a binder, and more than 5% has an adverse effect on corrosion resistance. The stable range of colloidal silica is pH 2.7 to 3.1 or pH 9.0 to 9.8, and the function of alumina cement as a gelling aid is that Ca0A203, the main constituent mineral in alumina cement, gradually increases. When dissolved in the sol, the pH value becomes high, and when the pH value exceeds the sol stabilization region, it becomes a gel.

If the content of alumina cement is less than 0.5%, it will take time to gel and it will be difficult to remove the mold, and if it exceeds 5.0%, it will reduce corrosion resistance, promote dissociation of zircon, and cause oversintering. This can cause spalls.

In addition, in the fire-resistant castable of the present invention, it is effective to add condensed phosphate as a peptizing agent to increase fluidity, and to add calcium hydroxide or boric acid as a PH adjusting agent to adjust gelation time. It is.

In addition, using vapor phase silica fume as an auxiliary binder has the effect of increasing fluidity and filling properties.
The amount added is preferably 2 to 3%, but even if it is not added, the properties of the refractory castable of the present invention will not be impaired. However, if it is more than 6%, the corrosion resistance will decrease and the alkali content in the silica fume may be affected. Promote the dissociation of zircon,
It becomes oversintered and causes spalling.

A lance is usually shaped like a cylindrical pipe through which a pipe for injecting flux passes inside, but cracks often occur due to the difference between the thermal expansion of the pipe and the thermal expansion of the furnace material due to heat load. Peeling from the parts and penetration of molten steel are likely to occur.

In order to prevent this, it is known that imparting residual expandability after heating is effective.

In the present invention, in order to provide this residual expandability, aggregates that have expandability due to transfer, such as silica or loite, are added. Therefore, significant strength deterioration occurs at temperatures below sinterability, that is, 500°C - i ooo°C. However, in the present invention, colloidal silica is used as a binder, and the strength is 0.01 - 0.0
2 Roux ultrafine colloidal silica particles contribute to the bonding of expandable aggregate and matrix fine powder raw material, thereby suppressing strength deterioration.

The amount of silica stone and lowite added is 3 to 40%, preferably 5 to 2%.
It is 0%. If it is less than 3%, the expansion property will be low and there will be no effect of preventing crack generation, and if it exceeds 40%, the corrosion resistance will decrease.

Note that adding stainless fiber to the refractory castable of the present invention brings about favorable effects in increasing bending strength and improving strain resistance, but the amount added is preferably 2 VOL% (5 wt%) or less. With -E, the effect does not increase, but rather has negative effects such as insufficient filling due to poor fluidity.

(Example) Next, Table 1, which reports examples of the present invention, shows the formulations of each refractory castable of Examples and Comparative Examples, and Table 2 shows the chemical analysis values of the raw materials used for each of these refractory castables. It shows.

Example-1 is an example in which the amount of zircon is large. In Comparative Example-1, cracks occurred due to residual shrinkage, and in Comparative Example-2, there was delamination, but in the case of this Example, There was no such problem, just smooth erosion, and the erosion speed was less than half that of conventional alumina castable.

Example-2 is an example of semizircon material, but Example-1
Although the erosion speed was faster compared to that of the previous model, no cracking or peeling occurred. In Comparative Example 3, no peeling occurred, but significant cracking occurred, and in Comparative Example 4, the corrosion resistance was poor.

Table-2 Chemical composition table of raw materials used (effects of the invention) The refractory castable for injection lance for out-of-furnace refining of the present invention has the following characteristics compared to conventional castable for lance:
■Decreases erosion in the slag line, extending service life.
It has the following effects: (1) No peeling occurs, eliminating the need for intermediate repairs; and (2) Reducing the unit consumption of furnace materials.

Claims (4)

[Claims] 1. Refractory castable for injection lance for outside furnace refining, consisting of refractory raw material mainly consisting of zircon, colloidal silica as binder, and alumina cement as gelling aid. 2. A refractory raw material made of zircon and/or a zircon raw material is used, and its content is ZrO_2 / SiO_2 amount of 5
2. The refractory castable according to claim 1, wherein the refractory content is in the range of 0 to 95%. 3. Colloidal silica as a binder with a solid content of 1-5%
using alumina cement as a gelling aid of 0.5 to 5
% of the fireproof castable according to claim 1 or 2. 4. 3 to 40% silica/lowite as residual expansion imparting material
The fireproof castable according to claim 1, 2 or 3, wherein the fireproof castable is used.